1. FIELD OF THE INVENTION
This invention relates to pulsed gas lasers, and more particularly, to method and apparatus for achieving the production of laser pulses with a high repetition rate in combination with good reproducibility by using laser gas media such as N.sub.2, Nc, Ar, Xe and He.
2. DESCRIPTION OF THE PRIOR ART
Several types of pulsed gas lasers have been described in various publications, see for example H. Gundel and W. Ross: "Zur Anregung ung Emission im N.sub.2 --Impulsgaslaser", Analer der Physik 7 (1974):3 p. 263-276. Said article compares a number of known nitrogen pulsed lasers. However, only a few papers deal with the electrical properties of such pulsed lasers, and to our knowledge, a numerical treatment of the relevant equivalent circuits is found in only one publication, namely Andersson and Tobin: "Electrical Breakdown in an Axial-field Nitrogen Laser", Physica Scripta, 9 (1974) p. 7-14.
Pulsed gas lasers, and particularly, pulsed N.sub.2 laser systems, are often used as dye laser excitation sources. To qualify as a good pumping source for dye lasers, the pulse to pulse reproducibility must be good; preferably better than 1% and the pumping laser must also have a pulse repetition rate capability of at least 100 Hz to facilitate proper sampling and signal extracting techniques. The fact is that in almost all applications of pulsed lasers, for instance in kinetic spectroscopy and fluorescence decay analysis as well as in the risetime calibration of fast detection systems, the pulse height and risetime reproducibility directly determine the accuracy and time resolution of the information obtained. Further the repetition rate to be used, must be maintainable during a full working day and not only for a couple of minutes.
Especially in axially excited pulsed gas lasers, it has so far not been possible to achieve good pulse to pulse reproducibility in combination with high repetition rate capability. Further, the maximum output pulse energy varies a lot between similar lasers. Those problems have been pointed out in said article of Gundel and Ross. Lack of good reproducibility is clearly seen if the laser pulses are recorded by sampling techniques. Such a recording, being typical for known lasers, is shown in FIG. 11 page 565 in a paper of Ericsson and Lidholt: "Generation of Short Light Pulses by Superradiance in Gases", Ark. Fys. 37 (1968) p. 557-568.
Therefore, clearly there is a need for high repetition rate pulsed gas lasers with good pules to pulse reproducibility.